A semiconductor device has a structure in which a semiconductor element is die-bonded to a mounting substrate by die bonding material. The semiconductor element is an LED (Light Emitting Device) and has a structure including an n-type GaN contact layer, a light emitting layer, a p-type AlGaN clad layer and a p-type GaN contact layer, which are epitaxially grown and stacked in this order on a crystalline substrate such as a sapphire substrate. The rear surface of the crystalline substrate is metalized by a metal laminate including a reflective layer and protective layer. The reflective layer may be made of, for example, Al or the like. When light from the light emitting layer is directed to the rear side of the crystalline substrate, the light is reflected by the reflective layer toward the front surface of the crystalline substrate.